The present invention relates to a retention for a support bearing so that axial shifting of the support bearing is prevented in a direction in which a bead-like bush endpiece may be drawn in a receiving lug.
In an installed state, a rubber bush of support bearings is subjected to shearing stresses. For the installation of the support bearing in a vehicle part, the bush has to be pressed with a tight fit into a corresponding receiving lug. For this, the rubber bush is introduced into the receiving lug with its bush endpiece facing away from the flange of the sheet-metal casing and resembling an annular bead, for which purpose the bush endpiece is correspondingly radially compressed. When the rubber bush reaches its final installation position, the annular bead-like bush endpiece extends out of the receiving lug, expands in the radial direction, engages over the edge of the receiving lug and thus forms an axial stop which, together with the flange of the rubber bush bearing against the opposite edge of the receiving lug, retains the rubber bush in its installation position. This axial stop, at the same time, forms a buffer for a stop plate which is arranged on a clamping screw passing through the bearing core and to be screwed together with the other vehicle part to limit the axial travel of the support bearing in one direction.
In support bearings installed in subframes with their axes in the vertical direction, the rubber bush is subjected to especially high stresses in the axial direction, i.e. shearing stresses. In this connection, it has been a surprising discovery to find that, under pronounced vertically relative movements between the subframe and vehicle body, the flange and annular bead-like bush endpiece can provide a reliable axial retention of the rubber bush. In contrast, the result of axially directed, high-frequency vibrations is that the rubber bush, although being mounted in the receiving lug with a high radial prestress, shifts axially in. The stop formed by the bush endpiece engaging behind the edge of the receiving lug and resembling an annular bead is thereby overcome, and the bush endpiece is undesirably drawn into the receiving lug. Consequently, the buffer member provided between the receiving lug and the stop plate arranged on the clamping screw is then absent, so that the bearing flexibility in the particular axial direction is correspondingly reduced. When there are vertical movements between the vehicle body and subframe, therefore, the stop plate strikes directly against the subframe even after only a relatively short axial travel, thus considerably restricting driving comfort.
A conventional support bearing is shown in GB2,122,555 A. In addition, U.S. Pat. No. 3,479,081 also describes a support bearing with a rubber bush having supporting elements which prevent the rubber bush from shifting axially in the orifice receiving the bush. The supporting elements form integral parts of a double-conical sleeve which constitutes the bearing core and the double cone of which is slotted along generatrices. The clamping screw passing through the sleeve is screwed into an internal sleeve thread. As a result of the tightening of the clamping screw, the sleeve ribs formed by the slot buckle, with the sleeve at the same time being shortened axially, and the rubber bush expands radially to such an extent that an axial movement in the orifices receiving it is no longer possible.
The screwing of the clamping screw together with the sleeve does not make it possible to fix the bearing core to a vehicle part with a specific pressure force. Moreover, in this bearing construction, it is not possible to equip the rubber bush with a sheet-metal casing. Finally, the axial flexibility is dependent on the radial bracing of the rubber bush.
German Patent Specification 960,401 shows how to retain an elastic plastic bush axially in the bore of a bearing body with a spring ring. For this purpose, a groove is formed both in the outer circumference of the bush and in the inner circumference of the bore of the bearing body. To mount the bush, the spring ring is inserted into its circumferential groove and compressed radially. When the grooves of the bush and of the bearing-body bore are located opposite one another, the spring ring springs open, and it is now in engagement half with one of the two grooves and half with the other.
A retention of this type is not practical for support bearings, since the sheet-metal casing provided on such bearings is either vulcanized onto the circumference of the rubber bush or vulcanized into this in such a way that only a thin rubber layer remains on this. A spring ring introduced between the rubber bush and receiving lug would therefore prevent the bearing from being removed because the sheet-metal casing would exert on the spring ring an axial force which would lead to a gripping between the wall parts of the two grooves preventing the spring ring from being compressed radially.
An object of the present invention is to provide a retention for a support bearing retention structure in which the bush endpiece is a circumferential groove into which, after the support bearing has been introduced into a receiving nut, a spring ring can be inserted to guarantee that, even under the influence of relatively high axially directed vibrations, the rubber bush can no longer shift in the receiving lug in the direction of the other vehicle part.
This object has been achieved in accordance with the present invention by further providing that the spring ring, in an inwardly spread state, has a diameter larger than the inside diameter of the receiving lug.
The spring ring inserted into the circumferential groove of the annular-bead-like bush endpiece engages over the edge of the receiving lug and thus prevents the bush endpiece from being drawn into the latter. At the same time, the circumferential groove can be formed in the bush endpiece on its inner circumference or on its outer circumference. In the former case, the dimensions of the spring ring must be such that, in the radially compressed state, its outside diameter, and in the latter case its inside diameter, is larger than the inside diameter of the receiving lug.